Whenever we build an engine, we always stop to examine each part’s specs, looking for seemingly minor upgrades over our current parts to save us from future headaches. And why not? After going through the trouble of removing the engine and tearing it down in the shop, now is the time to spend a few extra bucks on the simple touches, coatings, and upgrades that would be a lot of work to swap in later.
Plus, a few minor tweaks now can often future-proof the engine against future goals as well. One of the often-overlooked considerations in the course of a rebuild is various coatings and treatments on the engine’s valves — like the nitriding process on the Extreme Black Nitride valves from Howards Cams.
We’ve seen nitriding become popular on a number of mechanical components in the past decade or so. When we saw these valves from Howards, we wanted to know more about the Extreme Black Nitride valve-hardening process and how it will improve the quality and capability of these valves.
Nitrided valves have become popular recently but the process can also be found on crankshafts, camshafts, and various gears, as well as any moving engine and drivetrain parts that will benefit from improved strength, heat resistance, reduced friction, and an ultra-smooth finish.
Nitriding isn’t a patented process, but Howards Cams does it differently than its competitors. We checked in with Brian Adix, marketing manager of Howards Cams, to gain insight into how they do it and why it should be a serious consideration in your next performance cylinder head build.
“Most of our competitors have taken their street performance valve and modified it with a Nitride process,” says Adix. “At Howards Cams, we started with a clean slate, designing a true high-performance and race-application valve. To begin, we use high-nickel-content 21-4N forged stainless-steel pieces as a base. All-new blueprints for these valves were made in-house to make these able to handle the extreme stress of today’s high-performance, high-RPM race engines, as well as tuned and forced-induction engines too.”
Behind the Black: Gas Nitriding
Before getting into the meat and potatoes of these valves, we should discuss what, exactly, the nitriding process is, and how it justifies the extra costs involved. First of all, let’s get one thing straight; nitriding is NOT a coating. The nitriding process actually becomes part of the material being treated (in this case stainless steel alloy), which improves hardness, temperature-resistance, and reduces the coefficient of friction of these valves.
The nitriding process has been around for over 100 years and is essentially a heat-treating process that deposits nitrogen into the surface of the metal, hardening it. The nitrogen-disposition process is accomplished through one of three mediums: gas nitriding, salt bath nitriding, or plasma nitriding. For these valves, Howards uses the gas nitriding process, as it occurs at a relatively low temperature, which reduces the chances of any thermal distortion of the valve.
Once the nitrogen-rich gas penetrates the heated surface of the valve, a chemical reaction occurs where the nitrogen is stripped from the gas and combines with the steel to create a layer of nitrided steel on and immediately below the surface of the valve. That nitrided layer features a much higher surface hardness than the base material, along with greatly increased wear-resistance and a reduced coefficient of friction.
By reducing friction on the valve guide, the valves will not only run cooler throughout the RPM range, but will also reduce the engine’s frictional losses. However, the major benefit here is less wear and a longer valve lifespan — especially on high-RPM, and turbocharged, supercharged, and nitrous oxide-injected engines.
Besides the smoother-than-chrome finish improving air-fuel mixture flow into the cylinder head, the Howards Extreme Black Valve stems are also CNC-machined to be undercut, so the valves’ flow is further improved in all. Obviously, increased strength and reduced friction are benefits that justify an increase in cost. But just how much of a cost increase are we talking here? “To make it economical, you have to do large quantities per part number at a time,” says Adix. “These high quantities keep the price down, so [Howards] can price these valves as low — and often even lower — than many of our competitors’ non-nitrided valves.”
The increased longevity offered over traditional non-nitrided valves starts to pay off in both time and money quickly. The CNC-finished valves are milled to exacting tolerances for a true “drop-in and go” type of replacement. Currently, these valves are available for all Chevy small- and big-block engine applications, in both standard-replacement and extended stem-lengths. If you have special applications with high-flow aftermarket heads, the intake valves can be ordered in +.250-inch and +.350-inch lengths with exhaust valves in standard and +.100-inch lengths.
While the nitriding process has been around for over a century and certainly isn’t new to the automotive performance world, the process is enjoying a boom in popularity as of late. And really, why shouldn’t it? With so many positive attributes and few, if any, drawbacks (as long as the process is properly performed), the question becomes, what wouldn’t you want to nitride?